1. Field of the Invention
The invention relates to a cryogenic device of the type used in medical procedures.
2. The Prior Art
The use of cryogenic systems is most extensive in cryosurgical instruments for the treatment of cancer where they are successfully employed. Further medical ranges of application are for example general surgery, urology, gynecology, otorhinolaryngology and ophthalmology, plastic surgery, gnathosurgery, orthopaedics, veterinary medicine but also phytopathology and so on.
In known cryostats of this type, thermal insulation is achieved by the space provided between the housing and the inner container which contains the cryogenic medium, a vacuum with a residual pressure of approximately 10xe2x88x924 mm Hg to 10xe2x88x926 mm Hg being produced in the space. Cryogenic pumps as, e.g., activated carbon or zeolite, keep the above-mentioned residual pressure permanently constant as they sorb the residual gases from the vacuum space by freezing to low temperatures to xe2x88x92196xc2x0 C.
Connecting arrangements between the coaxial lines for the direct flow and the return flow of the cryogenic medium for cryosurgical interventions in the area of medicine, e.g., to connect a cryoapplicator to a cryoinstrument, are used just as extensively in the cryosurgical instruments used for the treatment of cancer. The sealing of a cryogenic medium by means of an intermediate layer, e.g., made of copper, is achieved by known connections of this type.
Known instruments of this type have the disadvantage that the stabilization of determined working conditions with excess pressure in a cryogenic system for cryogenic action upon the biological tissue as well as the proportioning of the cryogenic medium flowing toward the various-sized working surface of the cryoinstrument can be achieved neither with accuracy nor in a continuous and permanent way, so that it is not possible to maintain the temperature determined for cryogenic action in a continuous, permanent and accurate way, so that the accurate guaranteed cryodestruction of the diseased tissue, specifically of cancerous tissue, is not secured, thus leading to a recurrence (regrowth) of the tumor.
Another drawback is that, after some time, the cryogenic pumps with activated carbon or zeolite are filled up with residual gases, thus losing their adsorbing properties. In order to restore the adsorbing properties, the cryogenic pumps (activated carbon, zeolite) must be taken out, reactivated in vacuum by heating them up to high temperatures, and inserted again. A further disadvantage is that the heat flows from the bottle neck toward the inner container affect negatively the residual pressure in the vacuum space.
With the prior art devices it is equally disadvantageous that an intermediate layer for sealing the cryogenic medium can merely be used a few times, but not very often.
It is therefore the object of the invention to improve the prior art cryogenic systems in such a manner that under determined working conditions of a cryogenic system acting in a cryogenic way upon the biological tissue, an excess pressure is accurately achieved and maintained and that the proportioning of the cryogenic medium flowing toward the various-sized working surface of the cryoinstrument can be achieved.
It is therefore another object of the invention to improve the known cryostat in such a manner that the low pressure of residual gases (approximately 10xe2x88x924 to 10xe2x88x926 mm Hg) is permanently kept constant inside the vacuum space so that the cryogenic pumps must not be activated repeatedly and that the heat flows from the bottle neck toward the inner container are reduced.
It is therefore still another object of the invention to improve the known connections in such a way that a cryogenic medium is accurately sealed between the coaxial lines for the direct flow and the return flow of the cryogenic medium with an electric line for an electrical connection or interruption between both lines in the cryosurgical instruments, e.g., in case of frequent applications of various cryoapplicators and cryoinstruments.
The invention provides a cryogenic system with a regulating device for controlling the electromagnetic valves and the heating element, one electromagnetic valve being located at a distance from the connecting device and a heating element being located in the line for the return flow of the evaporated cryogenic medium, so that a determined temperature measured by the temperature detector is reached with an accuracy of xc2x11xc2x0 C. as a result of the opening and closing of an electromagnetic valve.
The invention provides for a cryostat used to keep permanently constant the low pressure of residual gases so that the necessary residual pressure is maintained.
An improved connecting device located between the coaxial lines for the direct flow and the return flow of the cryogenic medium has been developed and is used in cryosurgical instruments utilized for cryosurgical interventions in medicine, e.g., to connect a cryoapplicator to a cryoinstrument in the treatment of cancer.